How does TRADE work in the game?

[Belisarius Invictus]

Can someone tell me how the game figures out the trade routes and what is traded where for how much? I'm not talking about merchants, I'm talking about the basic "connections" over sea and land that you see all those ox carts and ships automatically moving around the map on. It seems like there's some sort of interesting mechanism behind it, and I'm curious if anyone has figured out how it all works...

[sapi]

I did a bit of digging in order to work out what effect the various trade buildings have on the value of a settlement's trade routes and I thought you might like to see the results.

The short answer is that anything in the building browser with the property "Increase in tradeable goods" will increase your trade income by 10% or 20% of the base value.

It's hard to tell how much extra money you'll make when you're choosing which building to construct next. However, the increase in trade value will affect all land trade and sea export routes in the settlement with the new building. It will also increase the value goods imported from this settlement by other settlements.

For example, if Bruge exports cloth to London then upgrading Bruge's Market to a Fairground will increase the value of London's sea import route from Bruge. (But not the other import routes in London.)

I you want to work out a settlement's total trade bonus then just add the bonuses for each building together. For example, if London has a Shipwright, a Great Market and a Merchant's Guild then the trade bonus is 90%. (30% + 50% + 10%) This means that the value of each trade route is 190% of the basic value. (i.e. 1.9 x base value) The bonuses are all listed in the table below.

Note that the bonuses aren't multiplied together. If you add Merchant's Wharf to London then the value of each trade route won't increase by 20%; it'll increase by a factor of 210/190. (about 10.5%)

A good strategy for maximising your income is build ports first and then the other improvements starting with the cheapest.

I don't know what determines the base value for each trade route.

I haven't looked at the effect of roads on trade.




The buildings listed in this table are the ones that are shown in the game with the property "Increase in tradeable goods". (This matches the "trade_base_income_bonus bonus" property in export_descr_buildings.txt.)

* I've checked the behaviour of most buildings but the ones I couldn't check are marked with a *.

# The "Sea Trade" buildings have the property "Trade fleets available x". As far as I can tell this has no effect on the value of trade. Does anyone know if this property does anything at all? (It maps to the "trade_fleet" property in export_descr_buildings.txt.)

enjoy,
Archie

Thanks Archie

[Belisarius Invictus]

Thanks for the info, but that's not quite what I was getting at.

I'm not so much interested in the "player perspective" of how to make the most money (percentage bonuses, etc), but rather, I'm curious how the game actually figures out that BRUGE trades CLOTH with LONDON, rather than something else with someplace else, and WHY... obviously it has something to do with the goods that Bruge and London have, but I'd really like to know the specifics of how the game figures out that since province X makes cloth, the cloth should pass through province Y, where it is put on a ship and is transported by sea to province Z.

[Belisarius Invictus]

Or, to ask about it a different way: there is a file called "map_trade_routes.tga". How is it used in the game??

[alpaca]

Not really sure but iirc each city can trade with each other city if it wants to (only one-sided restrictions for the number of trade routes) so the game uses the cities that generate the most income to trade with.
Which factors influence that, I have no idea though.

[Foz]

Not really sure but iirc each city can trade with each other city if it wants to (only one-sided restrictions for the number of trade routes) so the game uses the cities that generate the most income to trade with.
Which factors influence that, I have no idea though.

Well, some of them are obvious at least: trade route distance and the value of the resource(s) involved both seem to affect the value of the trade route. I would speculate trade rights do too, though IIRC you can't have trade with a nation you don't have trade rights with, so this is difficult to test - what seems clear is that you get more benefit from routes to other faction's provinces, which is likely the effect of trade rights with that faction.

As for determining the routes you get, I imagine there is a maximum distance that a trade route is allowed to span. With that knowledge, the game can determine how much profit you'd make from trading with each province that is in range, and order the list by profitability. Then it could select the top N of them to establish trade with, where N is how many trade routes the current settlement is allowed. In reality the problem is probably a bit more complex than this to solve completely since full trade routes would presumably eat 1 available fleet from each end of the route. This means that a route from Rennes to London for instance might be among the most profitable for Rennes, while London may be able to do far better than that if trading with the Danes. In that case it may be beneficial to accept a lower trade route for Rennes in order to give London more routes to Danish settlements. So in reality the game probably generates all possible trade route networks for your nation, and then selects the optimal configuration, since a settlement-centered view can easily lead to a less-than-optimal solution. I realize it sounds like a lot of work, but to current processors this is more akin to counting on one hand than anything else really...